[RFC PATCH 11/15] pwm: add the core infrastructure to allow atomic update

Boris Brezillon
2015-07-01T08:21:57Z

Add an ->apply() method to the pwm_ops struct to allow PWM drivers to
implement atomic update.
This method will be prefered over the ->enable(), ->disable() and
->config() methods if available.

Add the pwm_get_state(), pwm_get_default_state() and pwm_apply_state()
functions for PWM users to be able to use the atomic update feature.

Note that the pwm_apply_state() does not guarantee the atomicity of the
update operation, it all depends on the availability and implementation
of the ->apply() method.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
drivers/pwm/core.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++------
include/linux/pwm.h | 26 +++++++++++++
2 files changed, 124 insertions(+), 12 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 30631f5..6dafd8e 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -238,8 +238,9 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
unsigned int i;
int ret;

- if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
- !chip->ops->enable || !chip->ops->disable || !chip->npwm)
+ if (!chip || !chip->dev || !chip->ops || (!chip->ops->apply &&
+ (!chip->ops->config || !chip->ops->enable ||
+ !chip->ops->disable)) || !chip->npwm)
return -EINVAL;

mutex_lock(&pwm_lock);
@@ -430,7 +431,17 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
return -EINVAL;

- err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+ if (pwm->chip->ops->apply) {
+ struct pwm_state state = pwm->state;
+
+ state.period = period_ns;
+ state.duty_cycle = duty_ns;
+
+ err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
+ } else {
+ err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+ }
+
if (err)
return err;

@@ -455,6 +466,17 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
if (!pwm || !pwm->chip->ops)
return -EINVAL;

+ if (pwm->chip->ops->apply) {
+ struct pwm_state state = pwm->state;
+
+ state.polarity = polarity;
+ err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
+ if (!err)
+ pwm->state.polarity = polarity;
+
+ return err;
+ }
+
if (!pwm->chip->ops->set_polarity)
return -ENOSYS;

@@ -477,17 +499,27 @@ EXPORT_SYMBOL_GPL(pwm_set_polarity);
*/
int pwm_enable(struct pwm_device *pwm)
{
- if (pwm && !pwm_is_enabled(pwm)) {
- int err;
+ int err;

- err = pwm->chip->ops->enable(pwm->chip, pwm);
- if (!err)
- pwm->state.enabled = true;
+ if (!pwm)
+ return -EINVAL;

- return err;
+ if (pwm_is_enabled(pwm))
+ return 0;
+
+ if (pwm->chip->ops->apply) {
+ struct pwm_state state = pwm->state;
+
+ state.enabled = true;
+ err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
+ } else {
+ err = pwm->chip->ops->enable(pwm->chip, pwm);
}

- return pwm ? 0 : -EINVAL;
+ if (!err)
+ pwm->state.enabled = true;
+
+ return err;
}
EXPORT_SYMBOL_GPL(pwm_enable);

@@ -497,13 +529,67 @@ EXPORT_SYMBOL_GPL(pwm_enable);
*/
void pwm_disable(struct pwm_device *pwm)
{
- if (pwm && pwm_is_enabled(pwm)) {
+ if (!pwm || !pwm_is_enabled(pwm))
+ return;
+
+ if (pwm->chip->ops->apply) {
+ struct pwm_state state = pwm->state;
+
+ state.enabled = false;
+ pwm->chip->ops->apply(pwm->chip, pwm, &state);
+ } else {
pwm->chip->ops->disable(pwm->chip, pwm);
- pwm->state.enabled = false;
}
+
+ pwm->state.enabled = false;
}
EXPORT_SYMBOL_GPL(pwm_disable);

+int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
+{
+ int err = 0;
+
+ if (!pwm)
+ return -EINVAL;
+
+ if (!memcmp(state, &pwm->state, sizeof(*state)))
+ return 0;
+
+ if (pwm->chip->ops->apply) {
+ err = pwm->chip->ops->apply(pwm->chip, pwm, state);
+ if (!err)
+ pwm->state = *state;
+ } else {
+ /*
+ * FIXME: restore the initial state in case of error.
+ */
+ if (state->polarity != pwm->state.polarity) {
+ pwm_disable(pwm);
+ err = pwm_set_polarity(pwm, state->polarity);
+ if (err)
+ goto out;
+ }
+
+ if (state->period != pwm->state.period ||
+ state->duty_cycle != pwm->state.duty_cycle) {
+ err = pwm_config(pwm, state->period, state->duty_cycle);
+ if (err)
+ goto out;
+ }
+
+ if (state->enabled != pwm->state.enabled) {
+ if (state->enabled)
+ err = pwm_enable(pwm);
+ else
+ pwm_disable(pwm);
+ }
+ }
+
+out:
+ return err;
+}
+EXPORT_SYMBOL_GPL(pwm_apply_state);
+
static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
{
struct pwm_chip *chip;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index b47244a..7e99679 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -151,6 +151,29 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
return pwm ? pwm->state.polarity : PWM_POLARITY_NORMAL;
}

+/*
+ * pwm_apply_state - apply a new state to the PWM device
+ */
+int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state);
+
+/*
+ * pwm_get_state - retrieve the current PWM state
+ */
+static inline void pwm_get_state(struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ *state = pwm->state;
+}
+
+/*
+ * pwm_get_default_state - retrieve the default PWM state
+ */
+static inline void pwm_get_default_state(struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ *state = pwm->default_state;
+}
+
/**
* struct pwm_ops - PWM controller operations
* @request: optional hook for requesting a PWM
@@ -177,6 +200,9 @@ struct pwm_ops {
struct pwm_device *pwm);
void (*disable)(struct pwm_chip *chip,
struct pwm_device *pwm);
+ int (*apply)(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ const struct pwm_state *state);
void (*init_state)(struct pwm_chip *chip,
struct pwm_device *pwm);
#ifdef CONFIG_DEBUG_FS
--
1.9.1